Electronic voltage regulator circuit



P 22, 1953 D. c. cooK ET AL 2,653,235

ELECTRONIC VOLTAGE REGULATOR CIRCUIT Filed Jan. 5, 1946 7 22 mg u INVENTORJ, DAVID C. COOK CLARKE M. GILBERT aw/V 2M A TTORNE Y Patented Sept. 22, 1953 UNITED STATES PATENT OFFICE ELECTRONIC VOLTAGE REGULATOR CIRCUIT Application January 3, 1946, Serial No. 638,889

5 Claims. 1

This invention relates to electrical circuits, and more particularly to A. C. voltage regulators.

It is often desirable in certain electronic systems such as radio detection and ranging apparatus, television apparatus, and the like, to produce an alternating voltage of which the amplitude is fixed to a high degree of accuracy.

It is an object of this invention to provide a new and improved electronic voltage regulator; to provide a voltage regulator having an A. C. voltage output substantially constant Within wide ranges of input voltage; and to provide means for accomplishing the above objects which are simple and easily constructed.

Further objects, advantages, and novel features of the invention will become apparent from the description herein contained, in which reference is made to the accompanying drawing. The single figure of the drawing is a circuit diagram of the invention in its preferred embodiment.

Briefly stated, the described embodiment of the invention includes an overdriven amplifier whose input A. C. voltage may vary between wide limits; the output voltage of the amplifier approaches a square wave in shape, and further squaring and limiting is accomplished by networks associated with a cathode follower; the resulting square wave voltage of regulated amplitude is applied to a low-pass filter tuned substantially to the frequency of the input A. C.

. voltage; the filter output is a sine wave voltage of regulated amplitude, and is applied to a cathode follower circuit which functions as a matching justed to a desired amplitude.

Referring now to the drawing, the circuit reference point for the various voltages referred to hereinafter is designated by the conventional ground symbol. The various amplifiers or stages of the circuit are for convenience each hereinafter referred to by the same reference numeral as is applied to the vacuum tube associated therewith. A sinusoidal input voltage whose amplitude may vary may be applied to the illustrated embodiment of the invention at a terminal 5. This signal voltage is communicated to the conventional amplifier stage 6, which is preferably overdriven by the applied voltage. A nearly square wave output voltage of substantially fixed amplitude is thus developed across plate load resistor I. This output voltage may vary somewhat in both amplitude and waveform, but is at ;all times sufiiciently large to amply overdrive the succeeding stage. The output voltage of stage 6 2 is fed through condenser 8 and resistor 9 to grid iii of tube II.

The stage II is a cathode follower amplifier. Plate i2 of tube H is connected directly, as indicated by the arrowed lead 13, to the positive terminal of a source of direct current plate voltage (not shown), and the output voltage of this stage is developed across a cathode resistor M connected between cathode iii of tube It and ground potential.

The grid circuit of the cathode follower stage i I includes a diode tube It and a voltage dividing resistance network. Resistors I? and it are connected in series between the plate supply potential and ground, and a resistance 19 connects their junction to grid I0 of tube ii and to cathode 2i! of diode tube l6. Plate 2| of the diode tube is connected through resistance 22 to the plate voltage source, and to ground through a resistance 23. The functioning of the grid circuit of cathode follower stage II will become apparent hereinafter.

The output signal developed across resistance I4 is fed from cathode 15 to a series tuned circuit composed of inductance 24 and capacitance 25. The voltage developed across capacitance 25 of the series tuned circuit is sinusoidal and has a limited or regulated amplitude. This sinusoidal voltage is applied to the grid circuit of a conventional cathode follower stage including a tube 26 and a cathode resistor 28 of potentiometer type. The cathode follower stage 26 here functions as a high impedance load across capacitance 25 of the series tuned circuit, preserves the waveform of voltage developed across condenser 25, and enables a desired fraction of the capacitance voltage to be obtained without affecting the impedance load across the capacitance.

The output of stage ii approximates a square wave voltage, due to the overdriven action of the amplifier circuit. The grid circuit of tube 1 I further shapes this voltage into a substantantially square wave voltage whose amplitude is fixed at a constant value. Amplitude-limiting of the negative-going portion of the voltage at grid it is accomplished by diode 56. Plate 2i of diode i5 is held at a substantially fixed voltage by reason of its connection to the junction of voltage dividing resistors 22 and 23. The signal voltage at grid I0 is prevented from swinging much below the value of this fixed voltage, because the voltacross the grid circuit which limits the amplisquare wave developed across 'catii'oae resistc'r M. The maximum potential at grid ill may be prevented from exceeding the potential at plate i2 by properly proportioning the network of resistors ii, l8, and iii, with due consideration to the D.-C. voltage at the junction of resistors H and I8.

Condenser 8 is not essential to the proper operation of the circuit. Grid Hi may be connected to the plate of tube Ei through resistor 9. The maximum potential of grid It is in this instance prevented from exceeding the potential at plate 12 by appropriate choice of values for the network of resistors l, '9, H, i8, and

The input voltage to terminal '5 should be sufficiently large to overdrive stage 6, and may vary between wide limits. There is produced at grid in a square wave voltage controlled in amplitude within close limits. The voltage developed across cathode resistor l4 of cathode follower H is a square wave of regulated amplitude.

To obtain a sinusoidal voltage at the fundamental frequency of the input signal, a tuned filter circuit is employed as illustrated in the preferred embodiment wherein inductance 24 and capacitance 25 are tuned to substantially the fundamental frequency. The voltage fed to cathode follower stage 26 is taken from across condenser 25 to secure a low pass filter effect, and it istherefore a pure sinusoid of fixed amplitude determined by the amplitude of the square wave voltage developed across resistor It, An advantage of feeding the filter circuit from a cathode follower is that it provides a low impedance source for the filter circuit, and thereby the signal voltage across resistor M is substantially unaffected in waveform and amplitude by the presence of following circuits.

The amplitude-regulated voltage from condenser 25 is applied to the high impedance grid circuit of a conventional cathode follower stage utilizing a tube 26. A suitable fraction of the output voltage at cathode 21 may be obtained at a variable tap 29 of cathode resistor 28, so that the impedance of any following stage or device does not affect the circuit including condenser 25 and thereby destroy the filtering action or pass-characteristic of that circuit. Thus, a sinusoidal voltage is obtained between tap 29 and ground, having a selected and well-regulated amplitude.

It will be apparent to those skilled in the art that many variations of the circuit herein disclosed are possible without departing from the spirit of the invention. Therefore, it is not desired to restrict the scope of the invention to the precise embodiment herein disclosed.

What is claimed is:

l. A regulated, low impedance power supply 7 for obtaining an alternating voltage output of constant amplitude from an alternating voltage input of a single fixed frequency and varying amplitude, said supply comprising limiting means, means for applying said alternating voltage input as an input to said limiting means to obtain a fixed amplitude square Wave voltage as an output from said limiting means, filter means resonant at said fixed frequency, means applying said square wave voltage as an input voltage to said filter means to obtain a sinusoidal voltage output having said fixed frequency and a constant amplitude, impedance transform ing means having a high input impedance and a low output impedance to prevent loading of said filter means, and means applying said sinusoidal voltage output as an input to said impedance transformer means to obtain said alternating voltage output as the output of said impedance transforming means.

-2. A regulated, low impedance voltage source, as defined in claim 1, wherein said limiting means comprises an electronic tube voltage amplifier, wherein said varying amplitude alternating voltage input is applied as an input to said amplifier tube, the minimum value of said input being of 'sufiicient magnitude to overdrive said amplifier, a cathode follower circuit, means for applying the output of said amplifier as an input to said cathode follower circuit, and means coupling the output of said cathode follower "circuit to said filter means.

3. A regulated, low impedance voltage source as defined in claim 2, comprising means providing a first point of reference potential, means providing a second point of potential having a magnitude that is more positive than said first point, a unidirectional conducting device connected between said first point 'of potential and the input of said cathode follower, and resistive means connecting said second point of potential to said input of said cathode follower, said device being connected to become conductive when the potential at the input of said cathode follower is more negative than said first point of potential.

4. A regulated, low impedance voltage source as defined in claim 2, wherein said filter means comprises a series tuned circuit composed "of an inductance and capacitance tuned to substantially the fundamental frequency of said amplifier input, said filter means having an output voltage developed across said capacitance.

'5. A regulated, low impedance voltage scurce as defined in claim wherein said impedance transforming means comprises a second cathode follower tube, and means applying the output voltage developed across said capacitance as an input to said second cathode follower circuit, said alternating voltage output being obtai'n'ed as an output of said second cathode follower circuit.

DAVID c. 600K. CLARKE M. GILBERT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,200,055 Burnett May '1, 19 10 2,230,926 Bingley Feb. 4, 1941 2,340,364 Bedford Feb. 1, 1944 2,395,517 Stoller -r Feb. 26, i946 2,408,061 Grieg Sept. '24, 1946 2,544,226 Herold r Mar. 6, 1951 OTHER REFERENCES Transmissi'oh Networks and ave Filters," by Shea, published by vanNostr-ane o'o. ii-1 1929; page 29-1 reliedon. 

